auto merge of #14878 : vtsatskin/rust/rustdoc-sidebar-click-targets, r=alexcrichton

There was feedback gathered by @bjz which request for larger click targets in the rustdoc sidebar. Here's my attempt at that.

My only concern with this patch is the removal of `<br>` between sidebar links. This may break formatting for text-only viewers of this documentation. If there is a large enough demographic of people that will be affected, perhaps we can try switching the structure of each sidebar block sidebar to an `<ol>` with each item as a `<li>`. 

* Change links to display:block for click larger targets
* Remove linebreaks due to extra space
* Adjust margins so that element spacing stays the same
* Sidebar item hover background colour chosen from `<pre>` styling

src/librustdoc/html/render.rs

@@ -2001,7 +2001,7 @@ impl<'a> fmt::Show for Sidebar<'a> {
                 let class = if cur.name.get_ref() == item &&
                                short == curty { "current" } else { "" };
                 try!(write!(w, "<a class='{ty} {class}' href='{href}{path}'>\
-                                {name}</a><br/>",
+                                {name}</a>",
                        ty = short,
                        class = class,
                        href = if curty == "mod" {"../"} else {""},

src/librustdoc/html/static/main.css

@@ -154,25 +154,29 @@ nav.sub {
 
 .block {
     padding: 0 10px;
-    margin-bottom: 10px;
+    margin-bottom: 14px;
 }
 .block h2 {
     margin-top: 0;
+    margin-bottom: 8px;
     text-align: center;
 }
 
 .block a {
-    display: inline-block;
+    display: block;
     text-overflow: ellipsis;
     overflow: hidden;
     line-height: 15px;
-    padding-left: 5px;
-    padding-bottom: 6px;
+    padding: 7px 5px;
     font-size: 14px;
     font-weight: 300;
     transition: border 500ms ease-out;
 }
 
+.block a:hover {
+    background: #F5F5F5;
+}
+
 .content {
     padding: 15px 0;
 }

src/librustdoc/html/static/main.js

@@ -647,7 +647,6 @@
                 }
                 div.append($('<a>', {'href': '../' + crates[i] + '/index.html',
                                     'class': klass}).text(crates[i]));
-                div.append($('<br>'));
             }
             sidebar.append(div);
         }